The panel, set up to investigate ways of reducing red tape and bureaucracy, has made heads' workload a major priority in its second annual report, out today.
The report says the 10 per cent off-timetable period heads should have for PPA is simply not happening, with many teachers - particularly teaching heads - not receiving any leadership time at all. They say this is due to problems either in recruiting or funding cover for teachers.
"Heads have to plug the gaps and take over classes while teachers have their PPA time," said panel member Pat Clarke, head of St Mary's CA school, Wrexham.
Panel chairman Richard Edwards, head of Cardiff's Lansdowne primary school, said the panel had a lot of anecdotal evidence but few hard facts.
He said: "One of our priorities this coming year will be to gather evidence about heads' workloads. Then decisions will have to be taken by the department of education, lifelong learning and skills about any funding implications."
A survey conducted by the National Association of Headteachers Cymru in February found that 90 per cent of heads had seen their workload increase, and 31 per cent were covering for all or part of the non-contact time.
The union fears workload could be putting off teachers who are thinking of a move to senior management and headship. But the Assembly government says it has provided pound;70 million in 2006-7 for the workload agreement. It is working in tandem with the workforce agreement monitoring group and other agencies to address work-life problems in schools.